Diving into CentOS 7

[sudburr]

I’ve been quiet on the forums for a little while … busy time of year and all that with back to school.

I have a moment now where I’m re-deploying a few FOG servers and since Microsoft officially only publishes Linux Integration Services for Hyper-V for RHEL and CentOS, I figured I’d try my hand now at a CentOS 7 installation.

I’ve tamed Ubuntu and Debian for our FOG deployments. Wish me luck with CentOS!

[Wayne Workman]

You might find this helpful with your CentOS 7 journey, it’s all the same commands.

Fedora is also just beta for RHEL. Did you know that RH financially supports Fedora for their development environment/test bed ?

https://wiki.fogproject.org/wiki/index.php/Fedora_21_Server

[sudburr]

mmm, thx. I will keep an eye tilted to that document.

Interesting installer for CentOS.

[sudburr]

Am I correct?

By the looks of it, the command:

yum update -y

is the CentOS equivalent of what’s used by Ubuntu and Debian:

apt-get clean &&
apt-get update &&
apt-get upgrade -y &&
apt-get dist-upgrade -y &&
apt-get autoremove -y &&
apt-get autoclean -y &&

[Wayne Workman]

@sudburr said:

Am I correct?

By the looks of it, the command:

yum update -y

is the CentOS equivalent of what’s used by Ubuntu and Debian:

apt-get clean &&
apt-get update &&
apt-get upgrade -y &&
apt-get dist-upgrade -y &&
apt-get autoremove -y &&
apt-get autoclean -y &&

Not entirely. yum update -y simply updates all installed software that yum manages, including OS files.

yum clean all would clear out cache files and basically free up space, but the next update will be a little slower because it has to remake all that.

Here’s some info on it.
http://yum.baseurl.org/wiki/YumCommands

[sudburr]

Got it. Thx.

[sudburr]

Interesting. My CentOS installation is less than half the size of Debian.

2.3GiB vs 5.3GiB
P.S. I got it even further down to 1.66GB, but then aha. I switched from XFS file system to ext4 and it’s now 5.5GB.

[Wayne Workman]

@sudburr said:

Interesting. My CentOS installation is less than half the size of Debian.

2.3GiB vs 5.3GiB

… I’ve been advocating for Fedora / CentOS for a long time… lol

[sudburr]

I’ve run into my first problem with CentOS that I haven’t found a direct solution for yet. It’s a difference in syntax for ‘git’ compared to Ubuntu/Debian.

Git in Ubuntu/Debian allows me to direct clone and pull to a specific path (/opt/trunkgit) using:

git -C /opt/trunkgit clone https://github.com/FOGProject/fogproject.git /opt/trunkgit
git -C /opt/trunkgit pull

Git in CentOS doesn’t have a -C . For now I’m making do with

cd /opt/trunkgit
git clone https://github.com/FOGProject/fogproject.git

… but, git then creates the directory /opt/trunkgit/fogproject and downloads to that. For updating I must then:

cd /opt/trunkgit/fogproject
git pull

I like my scripts to have as few differences as possible between OSes so I’m looking for a way for git to perform the same in all three.

Pausing to reflect on what I just wrote … I realize I needed to think in the other direction. This works:

if [ ! -d /opt/trunkgit ]; then
mkdir /opt/trunkgit
fi
if [ ! -d /opt/trunkgit/fogproject ]; then
cd /opt/trunkgit
git clone https://github.com/FOGProject/fogproject.git
else
cd /opt/trunkgit/fogproject
git pull
fi
if [ ! -d /opt/trunksvn ]; then
mkdir /opt/trunksvn
fi
if [ ! -d /opt/trunksvn/fogproject ]; then
mkdir /opt/trunksvn/fogproject
fi
svn co https://svn.code.sf.net/p/freeghost/code/trunk /opt/trunksvn/fogproject

My brain is cooked… I spent too much time in the sun at a Canine Agility competition today.

[sudburr]

This leads me to my next task.

How to detect the OS variant. Namely Ubuntu, Debian or CentOS An if then idea.

[sudburr]

Looks like this might do it:

if [ -f /etc/debian_version ]; then
fi

if [ -f /etc/centos-release ]; then
fi

[sudburr]

Okay, next problem. I can’t get SELINUX to not start.

sed -i "s/=enforcing/=disabled/g" /etc/sysconfig/selinux
setenforce 0

… is not doing it. After reboot, sestatus shows SELINUX is still enabled.

[sudburr]

I see my mistake now. Though there is a /etc/sysconfig/selinux , I wanted to edit /etc/selinux/config .

To cover my bases I’m editing both. I suspect that the first is generated by the second:

setenforce 0
sed -i "s/=enforcing/=disabled/g" /etc/sysconfig/selinux
sed -i "s/=enforcing/=disabled/g" /etc/selinux/config

… and checking … yep, that did the trick.

Now for an actual Fog install.

[Wayne Workman]

@sudburr lol you’re so hardcore.

What’s wrong with using Vi and just opening the file and changing the “enforcing” to “disabled” ?? lol

and for the record, /etc/selinux/config is the only one you need to edit.

There is also a “permissive” mode for SELINUX. something to think about.

[sudburr]

Manually using VI is slow.

It’s far easier to simply copy and paste the command code in a single click.

Considering that disabling SELINUX is from your horses mouth, what’s the point of permissive?

[Tom Elliott]

VI can do copy and paste, for what it’s worth.

[Tom Elliott]

@sudburr And you can use sed statements in vi as well to change only the lines you need.

For example, instead of sed -i, in VI/VIM you would type:

:%s/=enforcing/=disabled/g

[Tom Elliott]

And to help a bit more in the understanding of SELinux and it’s modes: https://wiki.gentoo.org/wiki/SELinux/Tutorials/Permissive_versus_enforcing

[Wayne Workman]

@sudburr said:

Considering that disabling SELINUX is from your horses mouth, what’s the point of permissive?

For myself and many other people who have came to the forums in distress, FOG doesn’t fully work with SELinux in “enforcing” mode. However, it’s one of my goals to get fog to work with it turned on fully.

[sudburr]

Well I have FOG running happily on CentOS 7.1 now.

As much as enjoy Debian 8.2 over Ubuntu 14/15 now, I dare say I may prefer CentOS 7.1 now.